Radio frequency amplifying system



L. L. JONES RADIOFREQUENCY AMPLIFYING SYSTEM May 14, 1929.

Filed Aug.

INVENTOR Lesiar L. Jones ATTORNEY Patented May 14, 1929.

UNITED STATES LESTER L. JONES, OE ORADELL, NEW JERSEY.

RADIO FREQUENCY AMPLIFYING SYSTEM.

Application filed August 21, 1925. Serial No. 51,569.

This invention relates to a-u'dion or electron discharge tube amplifier circuits, and rel-ates more particularly toan improved. radio frequency audion amplifier system.

The prime desideratum of my present invention centers about the provision .of a radio frequency audion amplifying system in which the number of cascaded radio frequency stages or electron discharge tubes may be increased beyond that hitherto found possible or practical, the improved system of my invention being characterized by an amplification power substantially greater than that obtainable in radio frequency systems known to the prior art.

A further and correlated prime object of the invention comprises the production of an increased power audion amplifying system which is highly stable, which possesses the characteristics of ease of tuning and high degree of selectivity, with the use of a minimum number of control elements, and which is designed so as to permit facile control of the output volume without altering the tuning or affecting the stability of the system.

As is well known, radio or wireless receiving systems embodying radio frequency amplification commonly include two and sometimes three electron discharge devices or tubes which are employed as amplifiers of the radio frequencies, these tubes being interlinked or coupled by circuits which are tunable to a selected frequency. In the, most prevalent type of radio frequency system, all of the radio frequency coupled circuits are made tunable so as to be adjustable to the frequency which is to be transmitted through the system; and such systems are commonly known as tuned radio frequency systems.

It is now well recognized in the radio art that these tuned radio frequency systems are handicapped by serious limitations, prime among which is the inability or impractica bility of utilizing more than two radio frequency tubes in cascade without; creating reactions between the radio frequencycircuits which vitally interfere with the sta bility and amplifying ability of thesystem. These reactions are largely the result of feedback forces which produce a feedback of energy taking place through various channels, such as the coupling between the output and input circuits of a tube, which may for convenience be referred to as adjacent stage feed-back coupling, and the coupling between an input or/and output circuit of one tube across to the input circuit of a preceding tube, which may for convenience of description be referred to as a distant stage feed-back coupling.

These feed-back reactions existing in tuned radio frequency systems are, 'as

I for compensating for or neutralizing these feed-back reactions. It has been experimentallydetermined, however, that although the aforesaid adjacent stage feedback reactions can be-efiectively compensated for by means devisedfor the purpose,

the distant stage feed-backreactions incidentto multi-stage radio frequency sets cannot be controlled, so that it has been found impossible and impractical to build radio frequency systems with more than two efficient radio frequency tubes or to obtain additional amplification by a third radio'frequency tube.

I have discovered that these limitations inherent in tuned radio frequencysystems may be avoided by the cascading of untuned radio frequency stages onto tuned-radio frequency stages, and that the reactions between the stages may be so controlled asto permit the cascading of a large number of radio frequency tubes to produce a stable, radio frequency system. having an amplifying power substantially larger than, and as much as from 10 to 20 times greater than, that found in tuned radio frequency systems hitherto known. I

' It has heretofore been suggested to cascade an untuned radio frequency stage onto a preceding tuned radio frequency stage, but sys-v tems embodying such cascaded stages have been found too ineflicient for service, the prime reason beingthat the reactions introduced between the .untuned output and v a tuned input circuit were suchthat during the change of tuning oft-he input circuit and the system, the characteristic of the system would vary from that of too overdamped an input circuit to that of excessive oscillations,

the overdamping of the input circuit during the tuning process being so greatas to prevent the possibility of amplification, the

change from overdamping to excessive oscillations, moreover, preventing the employment of a controllable feed-back neutralizing system. As far as I am aware, the underlying reason for this change of characteristic of the system during the tuning process and the remedy for it has not been known.

I have empirically determined the character of the reaction taking place between the untuned output and the tuned input circuits of the transition tube, and have found that these reactions may be so predetermined or controlled as to inhibit the transition from excessive oscillations of the input circuit to the overdamping of the input circuit, and with the elimination of the transit-ion point, I am enabled to suitably neutralize the reactions so as to produce efiicient amplification, and so as to permit the cascading of a large number of radio frequency stages for the production of a high power amplifying set.

The principal objects of my present invention may therefore be said to include the provision of a high power radio frequency system; the more specific provision of a radio frequency system in which an untuned radio frequency stage or stages is or are cascaded onto a tuned radio frequency stage, with the reactions between the same controlled'to eliminate the de-s'tabilizing transition between the overdamping of the tuned stage and the production of excessive oscillations therein; the still further provision of a radio-f uency system of this character in which t e reactions between the untuned stage and the tuned stage are stabilized for the wholewave length range for which the system is designed; the still further provision of means for efficiently neutralizing these stabilized reactions whereby a system is produced having the characteristics of an amplifying power substantially greater than that heretofore known for radio frequency systems, and which system is further characterized by the pronounced stability of the circuits over the whole wave length range, the ease of tuning the same, the high selectivity obtainable with a smallnumber of tuning controls, and the ability to control the output volume of the system without altering the tuning characteristics of the receiving set.

To the accomplishment of the foregoing and such other objects as will hereinafter appear, my invention consists in the elements and their relation one to the other, as hereinafter more particularly described and sought to'be defined in the claims; reference being had to the accompanying drawings whichshow the preferred embodiments of my invention, and in which:

ig. 1 is a wiring diagrammatic view of a radio receiving system embod ing my lnvention, and showing one form 0 cascading and neutralizing control,

Fig. 2 is a wiring diagrammatic view of a modification, showing another method of cascading the circuits, and

Fig. 3 is a fragmentary wiring view of a modified form of control utilizable with either of the systems shown in Fig. l or 2.

Referring now more in detail to the drawings and first to Fig. 1 thereof, I show the invention applied to a radio frequency system having five radio frequency tubes or electron discharge, devices, designated sequentially as 1 R. F., 2 R. F., 3 R. F., 4 R. F., and 5 R. F., arranged in cascade and followed by an electron discharge device or tube employed as a detector and designated as Det., the system being capable of use with a loop antenna generally designated as Ant. Each of the electron discharge devices or tubes is of the three-electrode type having a filament, grid and plate, denoted respectively by f, g and p, with an exponent corresponding to the position of the tube in the series. The filaments are controlled by filament circuits all connected to the battery A, said filament circuits being denoted in Fig. 1 by F with an exponent corresponding to the position of the tubes, each of the filament circuits preferably including the resistance or rheostat r to 1" for regulating the intensity of incandescence of the filament,the rheostats r, r and r being preferably adjustable and the remaining rheostats being preferably fixed, for reasons that will appear clearer hereinafter.

The cascaded electron discharge devices each include input and output circuits designated as 2' and 0 respectively with an exponent corresponding to the position of the tube in the series, the first input circuit 2" being connected to the loop antenna Ant. and the last output circuit 0 including an audio frequency responsive device such as the telephones Tel., the remaining input and output circuits being interlinked or coupled together preferably by inductive means, the circuits being either transformer or impedance-coupled. As shown in Fig. 1 of the drawings, the output circuit 0 is coupled to the input circuit 2' by means of the transformer T having the primary P and the secondary S, and the output circuit 0 is coupled to the input circuit 2' by means of the transformer T having the primary P and. the secondary S while the remaining circuits are impedance-cou led, the circuits 0 and i being coupled by the impedance I, the circuits 0 and i by the impedance I and the circuits 0 and i by the impedance I The output circuits, as usual, include the battery B, which battery is connected as shown to the A battery.

As heretofore mentioned, the radio frequency amplifying system of my present invention embodies the cascading of one or more untuned radio frequency stages onto a the tuning process.

tuned radio frequency stage, with the reactions between the same controlled so as to eliminate the de-stabilizing transition which takes place during the tuning of the system and which has the effect of changing the characteristics of the tuned stage from that of being too overdamped to that of producing excessive oscillations, resulting either in such a large loss of energy as to render the system wholly ineflicient, or the production of a powerful disturbing reaction which. cannot be neutralized because of the transition of the characteristics of the tuned circuit during I have discovered that these disturbing changes in thecharacteristic of the tuned circuit during the-tuning of the same 'are due to the natural frequency constants ofthe untuned output circuit and its relation to the frequency range or wave length band through which the tuned stage is adjustable, and that by predetermining the natural frequency constants of the output circuit, the control of the reactions between the untuned and tuned stages may be ob tamed. More specifically, lhave found that the variation or transition from ovcrdamping to excessive oscillations of the tuned input circuit of the transition tube occurs over a narrow range of wave length about the natural free uency of the untuned transformer system, and that at reception frequencies higher than the natural frequency of the untuned output stage, the reaction is to produce a positive resistance in the tuned input stage over a wide range of the higher frequencies, and that at frequencies lower than the natural frequency of the untuned transformer:system or stage, the reaction is to produce a negative resistance in the input circuit over a large range of-frequency variation. In short, the natural frequency of the output stage is the transition or critical point, and the change or variation of frequency of the input or tuned stage from a. frequency above to a frequency below such natural frequencv produccsthe disturbing change of reaction.

To remed the defect I )roJose the )redey 7 l l l termining of the natural frequency of the output stage or circuit witlrrelation to the range of frequencies for which the system is to be designed, in a manner so as to prevent the production of any damping reaction. and so as to produce only an oscillation-creating feed-back reaction throughoutthe whole wave length or frequency range for which the system is built. By this means I am enabled not only to eliminate the transition or critical point. but to't'ix or stabilize the oscillations so that means may be employed for effectively neutralizing or balancing the same. To accomplish the desired results, I select the characteristics of the transformer or impedance coupling means for the untuned stage'such that the natural frequency of the untuned output circuit is greater than the With the system possessing this characteristie, a definite control may then'be introduced d to neutralize the ,feed-back-cre'ating oscillations through the whole range of frequenciesv which the system is capable of transmitting.

Referring now more in detail-to Fig. 1 of the drawings, I showthe untunedstage cascaded to the tuned stage embodied in the second radio frequency tube 2 R. F., the input circuit i of which is tunable through a predetermined wave length range'by means of an adjustable condenser C, the output circuit 0'- ofthis tube and the coupled input circuit i of the third radio frequency tube.3 R. F being non-tunable, these circuits being coupled by the trans former T 2 having a natural frequency incircuit greater than the highest frequency through which the input circuit is tunable. Viewed from another aspect, the natural wave length of the output transformer T in connected circuit or the natural wave length of the coupled circuits 0 -4 is smaller than the lowest wave length that can be transmitted through the system by adjustment of the input tuning condenser C. Viewed from still another aspect the arrangement is such that the load in the plate or output circuit ocombined with the load reflected thereinto by the subsequently coupled circuit i is an impedance having a natural wave length lower than the lowest wave length of the system, or conversely, having a natural frequency greater than the highest frequency to which the input circuit i is tunable. The transition tube is selected as the second radio frequency tube, so that an additional tuning control may be had, the same consisting in the adjustable condenser C arranged in parallel with the loop antenna for tuning the first inputflcireuit i to the selected frequency. With this ar-' rangement, the condensers C and C comprise the two tuning units for selecting the fre quency desired. 7

To obtain the most eflicient. results, the primary and secondary windings of the trans' former T? of the un'tuned stage should be as tightly coupled as possible; and with a, wave length range of 200-600 meters, itis of importance to keep down the distributed capacity of the windings to'a minimum, so

that a maximum reactance consistent with.

, therefore comprehendsaspa second step the est 1 provision of means associated witlif'the un p d-- m f *n tmli i o fb l ing nieans a substantially constant feed-back reaction at all wave lengths. The feed-fob these reactions.

'4- i p f1,713,132

erable. The use 1 of impedance. and transcascaded tuned circuits, the logarithmic dec former couplings in the system is-determined rement' increasing with the number of such by practical considerations. f tuned circuits. As explained in m afore- I have found empiricallythat when the mentioned copending application er. No. natural frequency of the untuned stage is thus 742,342, the insertion of the resistance R in selected and made greater than the highest the plate oroutput circuit 0*- has the effect frequency of the frequency range for, which i of absorbing or abstracting energy from the the system is tunable, that thereaction begrid circuit in proportion to and correspondtween the output-circuit of the transition ing with the energy retransfer or feed-back tube, such as'the second radio frequency tube that takes place from the output or plate of Fig. 1, to the tuned input circuitjthereof is circuit to thegrid circuit of the tube. The resubstantially constant over the whole wave length range. The constancy of the-reaction pending application, is preferably inducmay be explained as being associated with'the -tancefree so that all of the available inductendency of the input circuit to drop in resisttance may be conserved for the energy trans ancewhenthefrequencyisdecreased. Theposi fer from one tube to a succeeding tube, and tive resistance, therefore, I decreases, and the should be capacity-free so. that the resistance negative resistance of reaction also decreases may due to the drop in reacting voltage on the mize the decrease of plate voltage due to the plate, which in'turn follows from the decrease voltage drop in the plate circuit and so that of inductive reactance of the"plate :circuit. abalance for all-frequencies may be had.

.At the lower frequencies the net resultthere- .The use of this resistance or feed-forward fore is'probably to hold the input-circuit at a, formof neutralization is preferred for the substantially constant negative resistance. following reasons; i

It will be readily seen, therefore, that duel) No additional inductance or capacity is first to the stabilization of the reaetionbe :t-hefuntuned transformer circuit, so tween'the'untuned and the .tuned stage, and "th t one may design the transformer with a secondtoj the substantial constancyl; :of.; this. sllficie'ntly high rcactance to be effective for r a tion ova th wh le wav l ngth. ge,' developing the PliltGfCllCUlt energy in spite th a ti g-. r a bl 'dfd finit mnt l ofjthe limitation imposed that the natural and neutralization; My'. present invention fife uencyshould be greater than the highrequency of transmission.

2. The absence of tuning in this stage For neutralizing 'thfe stabi-- -1i d ti S; lm pl a y f g i ty ward resistance may therefore be leftsubof types of neutralizing systems'such' 'as" the s n lly n ant- Thisis an additional sistance R, as described in the aforesaid co-.

be .kept'as small as possible to'mini-- i ma ti nd iti f rm k qwn t th factor of stability to those enumerated in my July 9, 1925, for electron discharge tube am-- desirably is made variable in a'range ofwfromw the amplification constant thereof; and such art, butIprefer,lay-reasonoftheadvant'ages prior "applications, in which it wasehown hereinafterreferred to, to employ the'resistthat the feed-forward resistance was indeance or. feed-forward, pebfrieutralization P Q Q of tube plification nd tube described "and claimed ymelin my copend-i p l y. ing application Se'r, No 742,345? filed O t; 3. The slight voltage drop due to the feed- 8, 1924,}01- thod of and m an for' o t lforward resistance may be recovered and used ling nergy-fe dba k in. el ctron di ch r e cfl'ectively, as mthe output circuit for the devices, and application Ser. No. 42,399, filed -th1r d and fifthradio frequency tubes which are lmpedance-coupled, as will be hereinafter liher y t described, and have the feed forward resist- Th i t or f d-f d t f 'ance ncludedas part of the plate circuit load, neutralizing means comprises,*a's shown in as W111 QP out below- Even though Fi 1 f th d i rsistancgR'asso; the voltages across resistance and inductance ciated with the primary P of the untuned' add vectorially. there still remain substantial output tr n fo T hi h resistance h not gains in relation to the amplification oba value of the order of magnitude of the ratio talllable P tube h this yp of p i ierbetween the output impedance ofthe tube and In t other typ 0f k n u r lization methods, such incidentallosses could not be resistance is preferably about 1500 ohms, and 1 4:. It is probable that the phase of the am- 950 to I500 ohms so as to hold the inputcircuit plified output voltages is held to that causing 5- of the tube 2 R. F. with a slightpositive re minimum reaction on the tuned input circuits. sistance. For the purpose of telephony, the neutralizing resistance R isadjusted to give the input circuit 5 a damping factor of the. whole system with amplifications om logarithmic decrement .01 or .02, t is factor ten to twenty times higher than have b n of damping depending upon the number of previously obtainable,

It is only by some such explanation that I can Y account for the extremely high stability of which resistance may be of the order of 3,000

to 5,000 ohms. It is not essential that these feed-forward resistances be includedin each of the stages, and hence the same is merely shown embodiedin theoutputcircuits 0 and 0 Only a very considerable feed-back reaction through the untuned radio frequency tubes will create oscillation, so that the range of permissible feed-back reaction is large. The larger feed-forward resistances of 3,000 to 5,000ohm'sassociatedwiththe radio frequency tubes 3 and 5 are believed to be due to the larger inductances which are used or may be used in these stages. As already stated, when the circuits are impedance-coupled, the feedforward resistance, such as R, and the coupling inductance, such as I, together form the output loads, since a slightly higher of ficiency can be obtained by this means on the longer waves because the inductive reactance of the plate circuit inductance drops to rel- 'atively low values on the longer waves, so that the-voltage drop on the'feed-forward resistance becomes relatively appreciable. These two voltages are at-right angles, so that their sum is only the vector sum, yet in the practical case where the inductive reactance of the impedance I at the long wave may drop to say 3,000 ohms, and where a feed-forward resistance of 1,500 ohms is used, the vector sum becomes 3,300 ohms, resulting in a gain of 10% in efliciency of the amplifier. Preferably also the first input circuit 0 is provided with a small, such as a 1,000 ohm, feed-forward resistance R.

For controlling the output "olume of the system, the resistances 1 /1 and 1' are made adjustable as previously described, while the resistances or rheostats r and r are maintained constant, this method of controlling the volume being desirable for securing a volume control without affecting the stability or the tuning characteristics of the system. Thus it will be seen that a variation of the filament current of the second radio frequency tube 2 R. F. would result in slight detuning of its input'circuit due to the capacitive change from the feed-forward reaction. Also a variation of the filament current of the first radio frequency tube 1 R. F. would result in changes in the selectivity of the system due to, firstly, a change in the reaction through the first tube, and' secondly, to a change in the resistance'of the input circuit of the second tube due to the change in tube resistance across the primary of the tuned transformer T. The radio frequency tubes 35 however, by their filament current variation produce no change in tuning or in selectivity, but do produce a large variation in the volume of the system.

As an alternative form of volume control, I may employ the type of resistance neutralizing means shown in Fig. 3 of the drawings and described and claimed in my copending application 42,399 aforementioned, this comprising the provision of means for controlling .the energy output amplification or volume of the system simultaneously with the control of the stabilization thereof. More specifically, and referring to Fig. 3 of the drawings, the volume and stabilization control means comprises the coupling of an output circuit 0 of one tube to an input circuit '11 of a succeeding tube by means of a transformer such as T having a primary P and a secondary S and,

associating with the transformer primary P,

a potentiometer generally designated as Pot. which preferably comprises a resistance element arranged across and preferably in shunt,

with the transformer primary P and a movablecontact element it connected to the plate of the first tube and movable along the potentiometer resistance, movement of the contact along the potentiometer resistance having the 9 effect of controlling the feed-back and feedforward react-ions and the selectivity of the amplifier as awhole, and of controlling the energy transmitted from the output circuit 0 to the succeeding circuits.

The input circuits 1;, i and 2' of the fourth and fifth radio frequency tubes and the detecting tube are each desirably provided with a leak resistance designated respectively as Z, Z and Z each being of the order of a megohm. Also desorably a condenser 0 of the order of one-half a. microfarad is placed in shunt with the battery B, and a condenser c of the order of .005 microfarads is placed in the last output circuit 0 in shunt with the B battery and plate 50". Preferably also coupling condensers 0 c and c are provided in the input circuits 2', 71" and 2'.

Referring now to Fig. 2 of the drawings, I show a modification of the system, in which instead of cascading a plurality of untuned stages to a tuned stage, as shown in Fig. 1, the tuned and untuned stages are arranged in alternating relation. This system shown in Fig. 2 alsocomprises a plurality, such as 6 tubes, arranged in cascade or series, and including five radio frequency tubes and a detecting tube'designated sequentially 1 R. F., 2 R. F. 3 R. F., 4 R. F., 5' R. F. and Det., each tube including the three electrodes, the filament, the grid and the plate designated with reference characters corresponding to those of Fig. 1 of the drawings. The other corresponding parts, such as the A and B batteries,

the filament circuits, the filament rheostats,

the input and the output circuits, are similarly provided with corresponding .reference characters.

To alternate the tuned and untuned stages the first input circuit 71 of Fig. 2 is made tunable by means of the variable condenser 0" and the next stage comprising the output circuit 0-input circuit'z' is made non-tunable, these circuits being coupled by the transformer T the third stage comprising the output circuit 0 and the input circuit 2' being in turn made tunable by means of the condenser 0 connected in shunt with the secondary of the coupling transformer T the'fourth stage being in turn non-tunable and comprising the output circuit 0 and the input circuit 6* coupledby means of the impedance 1*, while the fifth and sixth stages are made tunable and non-tunable respectively, the fifth stage comprising the coupled circuits 0* and 13 coupled by means of the transformer T across the secondary of which isthe tuning condenser C the circuits 0 and i being in turn coupled by means of the impedance 1 The transformer and impedance coupling devices may be varied as desired, the same being shown to exemplify both methods of applying the inductive coupling between the circuits.

In the form of the invention shown in Fig. 2, each of the untuned output circuits is constructed to have a natural wave length lower than the lowest wave length for which the other circuits are tunable, embodying the first principle of the present invention, and each of these untuned circuits is provided preferably With the feed-forward type of resistance neutralizing means, the same being shown as the variable resistance R for the untuned output circuit 0, R for the untuned output circuit 0 and the variable resistance R for the untuned outp'utcircuit o Desirably also some of the tuned circuits may be provided with feed-back neutralizing means such as the resistance R" associated with the primary of the transformer T The system shown in Fig.2 may be used with a loop or other type of antenna designated as Ant., to which the system r i iay be coupled by means of the transformer The principle of operation of my improved radio frequency system and the many advantages thereof will in the main be fully apparent from the above detailed description thereof. In either of the modifications illustrated, an untuned stage, such as the output stage of the second radio frequency transformer 2 R. F. (Fig. 1) is cascaded onto a. tuned stage such as the tuned input circuit 1? of the radio frequency tube, the output circuit having a nat ural frequency greater than the highest frequency for which the tuned input circuit is adjustable. By the provision of this means, the reactions between the untuned stage and the tuned stage are stabilized and rendered constant so that the same may be controlled crto devised. The cascaded circuits are,

moreover, so interrelated as to produce a highly stable radio receiving set, with a high degree of selectivity obtainable with the employment of two control elements C and C, the system being designed so as to permit facile control of the output volume by simultaneous or other adjustment of the filament rheostats 1*"7* without altering the tuning or affecting the stability of the system as a whole.

For a further understanding of the advantagcs of the system embodying my present invention, the same may be compared with the tuned radio frequency systems of known types and the limitations thereof. As here tofore pointed out, due to the feed-back reactions incident to tuned systems, it is impossible to obtain any further amplification by utilizing a third radio frequency tube,

whereas with the employment of the principles of my invention I am enabled to produce a very stable and high-powered set with as many as five radio frequency tubes in cascade.

The reasons underlying the larger possibilities of a system embodying the present invention are manifold. Where additional amplification was sought by tuned amplification, there occurred in the output circuit relatively high oscillatory currents, because the last R. F. output circuit secured its voltage gain through resonance. The amount'of kinetic energy stored'in this last tuned circuit is therefore much greater than would be stored in an untuned output circuit having equal amplification. Another factor is concerned with the phase of the reaction. Obviously, to generate oscillations in the initial input circuit, the reacting voltages must serve to assist the currents flowing. Now when the latter input circuits are tuned, the phases of their currents are sharply varied as the circuits are adjusted in the region of resonance. This follows because these circuits usually have low resistance, so that a slightpreponderance of capacitive or inductive reaction shifts the phase abruptly through 180. Therefore in tuning the eascade tuned system, one is bound to strike an adjustment in the very near resonance region at which the' reaction produces oscillation. This appears clearly from the manipulation of a three-step cascade tuned amplifier re ceiver, because it has been found that when be secured. Such an adjustment, however, is not practical, as a slight variation in battery voltage, for example, is suflicient to destroy the balance.

In the system of the present invention, however, the lack of resonance currents in the untuned amplifier transformers produces minimum kinetic energy for retransfer, and the phase of the reacting forces is left constant, and probably this combination tends to produce a minimum oscillation-producing force.v Moreover,- where the last two stages are untuned, the successive grids have exactly opposite voltages differing only in magnitude by a factor of approximately 3 to 1. The lower voltage being near the input, the re sulting reaction is therefore less than twothirds that due to the last grid alone. The

' amplification that may be secured on the short wave band with the untuned transformer is usually less than the amplification constant of the tube, and is less than that obtainable .with a tuned stage, but owing to the fact that the increase in voltage with cascade untuned transformer circuits is geometric, it will be seen that two untuned stages will perform the work of one tuned stage, and due to the capability of cascading a large number of untuned stages with the employment of the principles of my invention, it will be readily seen that in the system of my invention from six to twenty times as much amplification as was obtainable in the prior types of tuned radio frequency systems may be had with the use of similar engineering precautions.

While I have shown my invention in the preferred forms, it will be apparent that many changes and modifications may be made in the structure disclosed, without departing from .the spirit of the invention, defined in the following claims.

I claim:

1. An amplifying system comprising an electron discharge device having an input circuit and an output circuit capacitivelycoupled by means of said'device to the input circuit, means for tuning the input circuit through a predetermined range offrequencies, the output circuit being untuned and embodying non-tunable coupling means, coupling the same to a subsequent circuit, said untuned output circuit in the combination wi th the subsequentlycoupled circuit having a natural frequency greater than the highest frequency of the whole frequency range through which the input circuit is tunable whereby the reactions of the output circuit on the input circuit due to the said capacitive coupling are fixed for the whole frequency range.

2. A radio frequency amplifying system comprising an electron discharge device having an input circuit and an output circuit capacitively coupled by means of said device to the input circuit, means for tuning the input circuit through a predetermined range of radio frequencies, the output circuit being untuned and embodying non-tunable induc-,

tive coupling means, coupling the same to a subsequent circuit, the load of said output circuit together with the load reflected thereinto by the said subsequently coupled circuit comprising an impedance having a natural frequency greater than the highest frequency of the whole frequency range through which the input circuit is tunable whereby the reactions of the output circuit on the input circuit due to the said capacitive coupling are fixed for the whole frequency range.

3. An amplifying system comprising an electron discharge device having an input circuit and an output circuit, means for tuning the input circuit through a predetermined range of frequencies, the output circuit being untuned and embodying means for coupling the same to a subsequent circuit, the load of said untuned output circuit combined with the load reflected thereinto by-the subsequently coupled circuit comprising an 1mpedance having a natural frequency greater than the highest frequency of the whole frethe output circuit to the input circuit are produced for the whole frequency range, and means for controlling the feed-back reactions.

4. An amplifying system comprising an electron discharge device having an input circuit and an output circuit, means for tuning the input circuit through a predetermined range of frequencies, the output circuit being untuned and embodying means for coupling the same to a subsequent circuit, the load of said untuned output circuit combined with the load reflected thereinto by the subsequently coupled circuit comprising an impedance having a natural frequency greater than the highest frequency of the whole frequency range through which the input circuit is tunable whereby energy feed-back from the output circuit to the input circuit is pro duced for the whole frequency range, and means for producing an energy feed-forward from the input to the output circuit to neutralize said feed-back of energy.

5. An amplifying system comprising an electron discharge device having an input circuit and an outputcircuit, means for tuning the input circuit through a predetermined range of frequencies, the output circuit being untuned and embodying non-tunable inductive coupling means for coupling the same to a subsequent circuit, the load of said untuned output circuit combined with the load reflected thereinto by the subsequently coupled circuit comprising an inductive impedance having a natural fre uency greater than the highest frequency 0 the whole range of frequencies through which the input circuit -is tunable whereby energy feed-back from the output circuit to the input circuit is produced for the whole frequency range, and means for neutralizing such feed-back of energy.

6. An amplifying system comprising an electron discharge device having an input circuit and an output circuit, means for tuning the input circuit through a predetermined range of frequencies, the output circuit being untuned and embodying means for coupling the same to a subsequent circuit, the load of said untuned output circuit combined with the load reflected thereinto by the subsequently coupled circuit comprising an impedance having a natural frequency greater than the highest frequency of said predetermined range of frequencies whereby energy feed back from the output circuit to the input circuit is produced for the whole frequency range, and resistance means located in the output circuit having a value .of the order of magnitude of the ratio of the output impedance of the device and the ampliii-ation constant thereof for producing an energy feedforward from the input to the output circuit to neutralize said feed-back of energy.

7. An amplifying system comprising an electron discharge device having an input circuit and an output circuit, means for tuning the input circuit through a predetermined range of frequencies, the output circuit being untuned and embodying means for coupling the output circuit to a subsequent circuit, the load of said untuned output circuit combined with the load reflected there-- into by the subsequently coupledcircuit comprising an impedance. having a natural frei the whole frequency range, and a resistancein said output circuit for producing an en ergy feed-forward from the input to the output circuit to neutralize said feed-back of energy.

8. An amplifying system comprising an electron discharge device having an input circuit and an output circuit, means for tuning the input circuit through a predetermined range of frequencies, the output circuit' being untuned and embodying a plate circuit and means for coupling the plate circuit to a subsequent circuit, the load of sald untuned output circuit combined with the load reflected thcreinto by the subsequently coupled circuit comprising an impedance having a natural frequency greater than the highest frequency of said predetermined range of frequencies whereby energy feedback from the output circuit to the input circuit is produced for the whole frequency range, and a capacity and inductance free resistance in the plate circuit for producing an energy feed-forward from the input to the output circuit to neutralize said feed-back of energy.

9. A cascade amplifying system comprising a pair of electron discharge tubes, each having'input and output circuits capacitively coupled by the tube structure, the output circuit of the first tube being coupled by nontunable means to the input circuit of the second tube, means for tuning the input circuit of the first tube through a predetermined wave length band, the said non-tunable coupled circuits having a natural wave length smaller than the lowest wavelength of said wave length band whereby the reactions of said non-tunable coupled circuits on the tunable input circuit due to the capacitive coupling therebetween are fixed over the Whole wave length band of the tunable input circuit..

10. A cascade amplifying system comprising a pair of electron discharge tubes, each having input and output circuits capacitively coupled by the tube structure, the output circuit of the first tube being coupled by nontunable inductive means to the input circuit of the second tube, means for tuning the input circuit of the first tube through a predeterminedwave length band, the said non-tunable coupled circuits having a natural wave length smaller than the lowest wave length of said wave length band whereby the reactions of said non-tunable coupled circuits on the tunable input circuit due to the capacitive coupling therebetween are fixed over the whole wave length band of the tunable input circuit.

11. A cascade amplifying system comprising a pair of electron discharge tubes, each having input and output circuits, the output circuit of the first tube being coupled by nontunable means to the inputcircuit of the second tube, means for tuning the input circuit of the first tube through a predetermined wave length band, the said non-tunable coupled circuits in coupled combination having a natural wave length smaller than the lowest wave length of said wave length band, whereby energy feed-back from the output to the input circuit of the first tube is produced for the whole wave length band through which the input circuit is tunable, and means for neutralizing such feedback of energy.

12. A cascade amplifyin system comprising a pair of electron disc arge tubes, eachhaving input and output circuits, the output circuit of the first tube being coupled by nontunable means to the input circuit of the second tube, means for tuning the in ut circuit of the first tube through a pre etermined wave length band, the said non-tunable coupled circuits in coupled combination having a natural wave length smaller than the lowest wave length of said wave length band whereby energy feed-back from the output to the input circuit of the first tube is produced for the whole wave length hand through which the input circuit is tunable, and a resistance in the plate circuit of the first tube having a value of the order of magnitude of the output impedance of the tube divided by the amplification constant thereof for producing an energy feed-forward in the first tube to neutralize the feed-back-of energy therein.

13. A cascade amplifying system comprising a pair of electron discharge tubes, each having input and output circuits, the output circuit of the first tube being coupled by nontunable means to the input circuit of the second tube, means for tuning the input circuit of the first tube through a predetermined wave length band, the said non-tunable coupled circuits in coupled combination having a naturalwave length smaller than the lowest Wave length of said Wave length band whereby energy feed-back from the output to the input circuit of the first tube is produced for the whole wave length hand through which the said input circuit of the first tube is tunable and means for producing a feed-forward of energy from the input to the output circuit of the first tube to control said feed-back of energy.

14. An amplifying system comprising an electron discharge tube having an input circuit and an output circuit capacitively coupled by means of the tube structure to the input circuit, means for tuning the input circuit through a predetermined range of frequencies, the output circuit being untuned and embodying an untuned stage having nontunable coupling means for inductively coupling the same to a subsequent-circuit, means for producing regenerative feed-back reactions'of said untuned output circuit on the tuned input circuit due to the capacitive coupling therebetween for the whole predetermined frequency range, and means for neutralizing such regenerative feed-back reactions. 1

15. A radio frequency amplifying system comprising an electron discharge device having an input circuit and an output circuit capacitively coupled by the device to the input circuit, means for tuning the input circuit through a predetermined range of radio frequencies, the output circuit being untuned and embodying Iransformer means non-tunably coupled to a subsequent circuit, means for producing an energy regenerative feedback reaction -from the untuned output circuit to the input circuit for thewhole frequency range and means for neutralizing said feed-back reaction.

16. A radio frequency amplifying system comprising an electron discharge device having an input circuit and an output circuit capacitively coupled by the device to the input circuit, means for tuning the input circuit through a predetermined range of radio frequencies, the output circuit being untuned and embodying a transformer non-tunably coupled to a subsequent circuit, means for producing an energy regenerative feed-back reaction from the untuned outputcircuit to the input circuit for the whole frequency range and resistance means associated with the primary of the transformer for neutralizing said feedback reaction.

17. A cascade radio frequency amplifying system comprising a pair of electron discharge tubes, each having an input circuit and an output circuit capacitively coupled by means of the tube structure to the input" circuit, means for tuning the ,input circuit of the first tube through a predetermined tralizing the said regenerative feed-back reactions.

18. A cascade radio frequency amplifying system comprising a pair of electron discharge tubes, each having input and output circuits, the output circuit of the first tube being coupled by non-tunable transformer means to the input circuit of the second tube, means for tuning the input circuit of the first tube through a predetermined range of radio frequencies and resistance means associated with said transformer means "and having a value of the order of magnitude of the ratio of the output impedance of the tube and the amplification constant thereof for producing a feed-forward reaction in the first tube for neutralizing for the feed-back of energy taking place from the said untuned output circuit to the tuned input circuit.

19. A radio frequency amplifying system comprising at least three electron discharge tubes in cascade, each havingan input circuit and an output circuit, means for tuning the input circuit of the first tube through a predetermined range of frequencies, transformer means coupling the output circuit of the first tube to the input circuit of the second tube and the output circuit of the second tube to the input circuit of the third tube. all said circuits save the input circuit of the first tube being untuned, and the untuned output circuit of the first tube having a natural frequency greater than the highest frequency of said predetermined range of frequencies through which the first input circuit is tunable whereby the reactions between the circuits of the first tube are fixed for the whole range of frequencies.

20. A radio frequency amplifying system comprising a pair of electron discharge devices in cascade, each having an input circuit and an output circuit, the output circuit of the first tube being inductively coupled to the input circuit of the second tube, means for tuning the input circuits of both tubes through a predetermined range of fre quencies, the output circuit of the second tube being untuned and embodying non-tunable coupling means for coupling the same to a subsequent circuit, said non-tunable coupling means in connected circuit having a natural frequency greater than'the highest frequency of said predetermined range of frequencies whereby the reactions between the untuned output circuit and the input circuit thereof are fixed for the Whole range of frequencies.

21. A radio frequency amplifying system comprising a pair of electron discharge devices in cascade, each having an input circuit and an output circuit, the output circuit of the first tube being inductively coupled to the input circuit of the second tube, means for tuning the input circuits of both tubes through a predetermined range of frequencies, the output circuit of the second tube being untuned and embodying non-tunable coupling means for coupling the same to a subsequent circuit, said non-tunable coupling meansin connected circuit having a natural frequency greater than the highest frequency of said predetermined range of frequencies, and means for neutralizing the feed-back reactions between the output and input circuits of the second tube.

Signed at New York city, in the county of New York and State of New York, this 19th day of August, A. D. 1925.

LESTER L. JONES. 

